VPN Speed issues using DD-WRT

Discussion in 'DD-WRT Firmware' started by Sbelew, Jun 26, 2006.

  1. Sbelew

    Sbelew Network Guru Member

    I was able to setup a vpn with using bits and pcs of posts here on this forum. My problem seems to be with slow speeds.

    My Setup; Work
    Windows XP Pro system using Windows VPN CLient connection, Bellsouth DSL 3.0/256k Internet

    WRT54G Router using DD-WRT v23 SP1 Final
    TampaDSL 3.0/768k Internet

    I am able to connect from work to home, browse all the network shares, view files, etc. But when I try to do something such as open a Word Document, a 3 page word doc with 2 color pictures, it took almost 2 minutes before i was able to view, scroll up and down through the document. Next I tried playing an MP3 file. The sound was very broken up. With these internet connections, do I have enough bandwidth to do these things, or is it possibly some incorrect settings someplace?

    In the router at home, I enabled the PPTP server, set the server IP to my static IP from my ISP, set a client IP range as to not conflict with anything on either network, put in the username and password in CHAP-Secrets. I also disabled the Loopback option.

    In my VPN connection at work under properties, networking, TCPIP properties,advanced I unchecked the use default gateway on remote network.

    That was pretty much it, it was a very easy to configure/setup process. I really like this new firmware. I was using the original Hyperwrt, then changed briefly to Thibor but was unable to get the WDS working. With this firmware, I had WDS up and functioning in about 10 minutes.

    Thanks for any help!
  2. sjdigital

    sjdigital Network Guru Member

    I have exactly the same problem, albeit with lower ISP connection speeds, so I thought I'd "bump" this rather than start a new thread. My home network has 4Mb cable connection with an upload speed of 400kb and testing it with speedtest.net would confirm these figures. But when I connect to it from afar and run speedtest.net it only manages about 300kb down and 100-125kbs up. One suggestion made on the dd-wrt forum board was that since the VPN was software rather than a specific hardware device this was the problem. Does that make sense? And if so, how can we improve things. And if not, ditto!
  3. docinthebox

    docinthebox LI Guru Member

    How about instead of running the PPTP server on the WRT54G, run the PPTP server on your PC instead (see http://www.nerdblog.com/2004/09/xp-has-built-in-vpn.html for how to set this up), and just set the WRT54G to do "PPTP passthrough".

    The other option would be to try a faster router that supports dd-wrt, like the WRT300N or WRT350N.
  4. sjdigital

    sjdigital Network Guru Member

    But the object of the exercise is actually to provide access to my NAS box without having to have a PC on. In fact there isn't a PC permanently attached to the home LAN - everyone at home has laptops! But would the 300N really be any better? Its processor is only slightly faster than the 54G - 264 vs 200/216. Hardly enough to make a real difference I would have thought.
  5. docinthebox

    docinthebox LI Guru Member

    The 300N and 350N use the BCM4704 and 4705 processors respectively. They're the top of the line processors from Broadcom, and are at least several years more advanced than the 4712 used in the WRT54G. It's not very meaningful to compare the frequency across processors of different architecture, different amount of data cache, and most likely different CMOS fab scales as well (e.g. 130nm, 90nm). It's like comparing P3 and P4 performance by looking at only the operating frequency. Also, if you look at the WAN to LAN throughput of the WRT54G, you know the BCM4712 is not powerful at all, because the WAN to LAN throughput basically reflects how fast your processor can run the firewall in getting packets from the WAN side to the LAN side.


    In fact, knowing the poor WAN to LAN performance of the WRT54G, I'm not surprised at all that when you load it even further by running a VPN server on it, you get quite pitiful performance.

    Look at Broadcom's official description of the 4705:


    "The Broadcom BCM4705 processor is the highest performance chip in the 802.11n/MIMO Intensi-fi processor family. It integrates a powerful 300 MHz MIPS32 core estimated at 500 DMIPS with 4-way set associative 32 KB instruction cache, a 32 KB 2-way set associative data cache, and a 4 KB prefetch cache. An enhanced 10/100/1000 GigabitEthernet MAC controller with TCP Segmentation and checksum Offload (TSO) hardware acceleration engine substantially enhances system throughput."
  6. sjdigital

    sjdigital Network Guru Member

    I appreciate your replies but I'm getting a bit lost here! If I can get close to the download and upload speeds quoted by my ISP using the WRT54G, then how significant are the WAN to LAN figures you refer me to? But regardless of that, are you in effect saying that running the dd-wrt PPTP VPN server is more than the WRT54G can cope with, at least in terms of providing decent throughput?
  7. docinthebox

    docinthebox LI Guru Member

    The WAN to LAN throughput tells you what's the fastest rate your router can run the firewall at. In a way, it's like a metric or benchmark, a very good one in fact, at evaluating the speed of your router processor. A router which can route packets from WAN to LAN at 100Mb/sec definitely has a much faster processor than one that can only route at 20Mb/sec. Basically, if your router has low WAN to LAN throughput, you know the router processor is slow. And when you run a VPN server on your router, the performance/throughput is directly dependent on how fast your router processor is, because basically what you're doing is increasing the workload the processor has to perform on each packet in getting it across from WAN to LAN.
  8. sjdigital

    sjdigital Network Guru Member


    Apologies for not acknowledging your last post but the email notification didn't tell me about it. I'm still trying to make sense of the figures, but even if my WRT54G can only manage 20Mbs WAN to LAN and vice versa, I'm still only getting 100kbs through the VPN which is a performance hit of over 200 to 1 (if my maths are correct!). Is that normal?
  9. docinthebox

    docinthebox LI Guru Member

    Try using OpenVPN instead of PPTP. If the speed is still slow for you, try a faster router.
  10. sjdigital

    sjdigital Network Guru Member

    Yes, the general consensus seems to be that OpenVPN is the best solution - the PPTP server works in theory but not very well in practice. But I can't try this out until I am next back at home and can recongfigure the router as for some reason it has stopped working and I had to get my daughter to stop by our house and replace it with my old SMC one so that we can at least use our Slingbox to watch TV from afar!
  11. docinthebox

    docinthebox LI Guru Member

    Also, which version of WRT54G do you have? If it's anything after v5, it only has 8MB RAM, and the performance may have been bound by memory. Try replacing it with the Buffalo WHR-G54S which has 16MB RAM.
  12. sjdigital

    sjdigital Network Guru Member

    Knowing that the later version of the WRT54G weren't as good, I sought out an earlier version and it's V 2.2 with 16MB of RAM. But as it's many miles away from me at the moment, any change to the VPN server will have to await my next trip home at the beginning of March
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